Many customers have been talking about (and showing me pictures of) plants that died over the winter, especially perennials. They can not understand why this happened since the winter was so mild. From what I can tell it seems to be due to what is called frost heaving.
Many customers have been wondering why some of their plants died during this very mild winter. Especially hard hit were perennials. Actually the weather this winter, with it's fluctuating temperatures, can be deadly to plants under certain conditions since it can cause a horticultural problem called frost heaving.
Frost heaving causes the roots and crowns of plants to be "pushed' out of the ground above the soil level, thus exposing them to the cold temperatures and harsh dry winds of winter. The heaving is the result of wide temperature fluctuations resulting in repeated cycles of freezing and thawing of the water in the soil causing it to expand and contract. These expansions and contractions push and turn the plants in the ground.
Most susceptible are plants with shallow root systems, and those that were recently planted and did not have time to develop an adequate root system.
What can be done to protect plants against frost heaving? The following are suggestions to help reduce the chances of frost heaving affecting your plants.
1. Be sure planting beds are well drained. Good drainage prevents water from pooling in the beds which results in soils that freeze and thaw repeatedly. Adding organic material such as compost loosens soil and encourages good drainage.
2. Do fall planting early, at least 6 weeks before the first autumn frost. This would allow plants to develop an adequate root system that will anchor them into the soil.
3. Mulch with organic material. Mulch helps moderate soil temperatures thus reducing the destructive expansion and contraction. Remember mulch should be applied after a hard frost.
4. Check on your plants periodically throughout the winter, paying particular attention to susceptible ones. Cover any roots found to be exposed with some topsoil.